Do you see that stapler? Convince me to buy it.

This is a test to see if you are an experienced salesperson. I do not have much sales experience but I would answer this question by thinking of salesman I encountered in the past that I felt was good. Think about your experience with sales people and list what they did. For example, they probably follow a format. First, they explain what the product is. Then they tell you the functionalities and where you can use it. Third, they should tell you how much easier it will make your work. Fourth, it should have a good warranty. The question didn't give you details. So feel free to make something up. It will show your creativity. Continuing, the product should have a good return policy. Finally, you can talk about the reduced price, or the price guarantee.

If you are applying for a sales position, you have to be ready to be able to sell anything in the room. I would recommend thinking about an outline. Get that in your head. Then use the outline to practice selling variety of things. You can use my answer as an outline covering features, functionality, safety, design, warranty, and price. But don't limit it to just these, if you have another idea, add it to this, or make up your own.